MAX is a transcription factor of the basic helix-loop-helix leucine zipper family that plays an important role in transcriptional regulation. It forms homodimers and heterodimers with other family members such as Mad, Mxi1 and Myc. Mutations in MAX lead to hereditary and sporadic pheochromocytoma and paraganglioma, which are neoplasms of the adrenal medulla that arise from chromaffin cells or neural crest progenitors. In immunohistochemistry of normal tissue, MAX has nuclear positivity in most tissues throughout the body, including dendrites in the brain. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; Clin Cancer Res. 2012 May 15;18(10):2828-37, PMID: 22452945; Pheochromocytoma and Paraganglioma. Endotext. 2018, PMID: 29465938;